Some vehicles may use bi-fuel engines operating on either a first gaseous fuel (such as compressed hydrogen, liquefied propane gas (LPG), or compressed natural gas (CNG)), or a second liquid fuel (such as gasoline). For example, engines may be bi-fueled with CNG-gasoline or LPG-gasoline. The above mentioned systems combust either the first fuel or the second fuel for engine operation. The fuels are injected either through a single injector or through different injectors into the combustion chamber of the internal combustion engine.
U.S. Pat. No. 7,228,841 describes a vehicle with an engine that uses gaseous hydrogen and gasoline. In this example, fuel is injected through two separate injectors into the combustion chamber. The fuel type is switched from one to the other depending on engine operating conditions, environmental conditions, and operator demand. For instance, if a storage level of gaseous hydrogen decreases below a predetermined amount or if it is determined that the vehicles has exited out of a city to suburbs, fuel supplied to the engine is automatically switched from gaseous hydrogen to gasoline.
However, the inventors herein have recognized disadvantages with such an approach. For example, if the vehicle has operated in city conditions for an extended duration, the hydrogen supply may be depleted. Thus, when starting the engine during subsequent operation, there may be an insufficient supply of hydrogen or hydrogen pressure to start the engine if it is desired to use gaseous fuel preferentially, even when the level of gaseous fuel in the tank is low.
In one approach, the above issues may be addressed by a method for controlling operation of an engine comprising delivering a gaseous fuel during a first operating range when an amount of stored gaseous fuel is greater than a threshold; and disabling the delivery of the gaseous fuel during the first operating range when the amount of stored gaseous fuel is less than the threshold and delivering a second fuel to operate the engine, yet continuing to deliver the gaseous fuel to start the engine during a cold start even when the amount of stored gaseous fuel is less than the threshold.
In this way, even when a supply of gaseous fuel is running low, gaseous fuel may be automatically and preferentially used for starting by disabling its use during the first operating range. In this way, it is possible to achieve a greater number of cold starts using the gaseous fuel. Such preferential use of the gaseous fuel for cold starts, rather than other engine running conditions, can be beneficial in reducing emissions. For example, emissions reductions can be achieved by using the gaseous fuel for starting rather than normal engine operation occurring after the emission system has reached its operating temperature.